Hardware adapters have been used in the communications field to accommodate the transfer of information between a communication transmission line and a data processing system. Changes in communication protocol have placed great demands on the adapters. Such demands have been met by increasing the amount of hardware, thereby increasing manufacturing costs and physical size.
The essence of communication is a concurrent bidirectional transfer of information. Hardware adapters have required two separate systems, one for receive operations and one for transmit operations. It also is recognized that messages may be varying lengths and may be comprised of data bytes of varying bit sizes. Hardware has provided a highly limited flexibility at high cost and space sacrifice. The potential for cost expansion of hardware functionality is low.
The problems associated with hardware communication adapters have been overcome partially by the advent of communication controllers comprised of hardware and some form of firmware control system. While the duplication of entire systems to accommodate both transmit and receive operations has been obviated, the amount of hardware used is still significant because of an inefficient marriage of firmware and hardware functionalities. This has resulted in somewhat of a compromise as to the information transfer rates that the system can handled.
Further, the data processing capacity of communication controllers have been relatively limited such that the accommodation of broadband communication links has been difficult, if not impossible.